allow double-click in file browser to load data files * files-dock-widget.cc (files_dock_widget::display_directory): If file looks like Octave data file, load it instead of opening with editor. * ls-mat-ascii.h, ls-mat-ascii.cc (get_lines_and_columns): New option to supress error messages. New option to check for numeric values. (looks_like_mat_ascii_file): New function. * load-save.h load-save.cc (is_octave_data_file): New function. (get_file_format): Don't return LS_MAT_ASCII unless the file really looks like it is a numeric data file.